1. Field of the Invention
The present invention relates to an image pickup apparatus including an image pickup element that captures a subject by controlling exposure to light incident through a lens by the use of a shutter.
2. Description of Related Art
In a single-lens reflex camera whose lens is exchangeable, when a subject, which is taken by reflecting light incident through a lens by a mirror, is observed directly (hereinafter, referred to as “finder photographing”) through a finder, a shutter unit placed in the vicinity of an image pickup element is moved by a shutter driving mechanism driven with a cam that functions in synchronization with a motor from a first stop position, at which the mirror is lowered from a shutter charge completion state so as to make it possible to observe the subject through the finder, to a third stop position, at which the shutter charge is released so as to lift the mirror further to a retracting position. At the third stop position, before the shutter charge is released, a first electromagnetic holding portion (solenoid) holding a first light shielding body (first shutter curtain) on an upper side and a second electromagnetic holding portion (solenoid) holding a second light shielding body (second shutter curtain) on an upper side are both energized, and the first light shielding body and the second light shielding body are both held on the upper side.
During exposure, the first light shielding body that opens an opening as a result of the cancel of the energization of the first electromagnetic holding portion runs downward, and the second light shielding body that closes the opening as a result of the cancel of the energization of the second electromagnetic holding portion after the elapse of a predetermined exposure time runs downward. The first light shielding body or the second light shielding body covers the opening at all times except for the exposure time, thereby blocking light incident upon the image pickup element.
Furthermore, recently, a camera (digital still camera) using an image pickup element is equipped with a high-definition liquid crystal monitor, thereby being able to display an image captured with the image pickup element. This enables not only the above finder photographing, but also “live view photographing” in which a subject can be photographed while being observed on a monitor.
During the live view photographing, the energization of only the first electromagnetic holding portion that holds the first light shielding body on the upper side is cancelled at the second stop position, whereby only the first light shielding body retracts downward. The second electromagnetic holding portion remains energized to keep the second light shielding body retracting on the upper side and maintains an opening state, whereby the shutter stops while light through the lens reaches the image pickup element at all times. Consequently, a video (through image) of a subject obtained from the image pickup element can be displayed on a monitor mounted on a camera body. The above configuration is disclosed by Patent Document 1 (JP 4-53408 A) and Patent Document 2 (JP 2006-184717 A).
However, according to the configuration disclosed by Patent Documents 1 and 2, the second light shielding body is kept retracted on the upper side after the first light shielding body retracts downward at the second stop position, so that the second electromagnetic holding portion needs to be energized continuously. Thus, there is a problem that the second electromagnetic holding portion is energized continuously during a live view mode, which increases the power consumption.
Furthermore, during the live view photographing state, the shutter is moved from the second stop position that is in the live view photographing state to the third stop position again through the first stop position during the period from a time when a release button is operated by a photographer to a time when exposure is performed, whereby a series of exposure operations are performed. After that, the shutter is moved to the second stop position through the first stop position, and stopped in the live view photographing state. Thus, there is a problem that it takes a very long period from a time when the release button is operated to a time when exposure is performed actually in the live view photographing state.